Recently, automation of the tape recorder has been advanced so that many tape recorders no force is needed for manual operation, and the change of various modes is effected only by extremely light operations, such as pushing switch buttons, by which the maintaining and the change of the modes are effected by utilizing the attractive force of electromagnetic plungers and the driving force of the motor.
In such widely automated tape recorders it is necessary to transfer working members to their predetermined positions by parallel displacement, and consequently to transform the rotating force of the motor to rectilinear motions. Usually a power cam is used as a transformation means for this purpose. This power cam is so constructed that it is rotated by the motor through a driving system consisting of a plurality of gears, which works and attracts a roller of a power plate only when the motor rotates in the normal direction, so that the power plate goes and returns and the members linked to the power plate effect parallel translation.
Moreover, this power plate is energized in the returning direction by a spring so that, when the power cam initially moves, it advances against the energizing force of this return spring, and when the power cam rotates further beyond the maximum cam diameter, it is returned by the energizing force of the return spring.
Consequently, the lead portion of the power cam has a long, slowly spirally varying curved surface, and as a result its return portion forms a short, rapidly varying curved surface so that the power cam can draw the power plate slowly, leaving always some surplus in available power, depending on the consturction of the power plate moving against the weight of all the elements and the force of the return spring.
Further, in an autoreverse type tape recorder, in which the tape moves both in the normal and in the reverse direction, the two reel bases, normal and reverse, for driving the tape in the normal and reverse directions are driven by a mechanism which is so constructed that the driving force of a motor rotating always only in the normal rotation direction is transmitted to two power gears, normal and reverse. These are engaged with each other so that they rotate always in directions opposite to each other, and the rotating force of these power gears is transmitted to either one of the reel bases, normal or reverse, by using a movable idler displaced according to the desired direction of movement of the tape.
In such a tape recorder, in order to satisfy the requirements of reduction of the size and system simplification, there is adopted a construction by which various sorts of working elements are moved by a driving system, which is in common to the driving system for the tape as stated above, and this latter driving system drives also, for example, the loading/eject mechanism.
Consequently, it is necessary to reverse the movement of the driving system for moving each of these, working elements in directions which are opposite to each other for loading and for ejection. For this purpose, heretofore, a commuting mechanism has been disposed in the train of the driving system. However, since the mechanism is complicated by this structure, recently a construction has been used wherein the necessity for a commuting mechanism is eliminated by use of a motor rotatable in both directions, i.e., normal and reverse.
Furthermore, in the tape recorder described above, the eject operation is effected preferably relatively slowly by the driving force of the motor, since the tape is easily charged with static electricity; hence, if the tape is loose, it is attracted by the journal of the capstan, the pack guide, etc. to be deviated from its normal path, which gives rise to the inconvenience that the tape is twisted, or folds are produced therein.
In order to solve these problems provoked by the looseness of the tape, heretofore there has been adopted a method by which before the eject operation the driving gear is engaged with both the reel bases, normal and reverse, so that both reel bases are rotated in the direction in which the tape is wound.
In a tape recorder which is so widely automated, for moving each of the working elements in the directions opposite to each other for loading and for eject, it is necessary to reverse the movement of the driving system. For this puspose, heretofore, a commuting mechanism has been disposed in the train of the driving system. However, since the mechanism is complicated by this structure, recently there has been adopted a construction by which the commuting mechanism can be omitted by using of a motor rotatable in both the directions, normal and reverse.
In addition, when the driving system is reversed in the reel base driving mechanism of the autoreverse type tape recorder described above, it has the following disadvantages.
That is, in order to reverse the driving system, there is adopted usually a construction in which the reel bases are isolated from the driving system by detaching the idler from the reel bases. However, in this case, since this detaching of the driving system from the reel bases is liable to be done imperfectly or with a delay, the rotation direction of the reel bases is reversed. On the other hand the normal rotation direction is the one by which the tape is wound by each of the reel bases. Consequently, when the rotation direction of each of the reel bases is reversed, since the reel bases rotate in the direction by which the tape is rewound, the tape is unwound, loosened, twisted or entangled on the way, which was a problem to be solved.
Furthermore, prior art tape recorders in which both the reel bases are rotated in the direction in which the tape is wound, have the following disadvantages.
In the method wherein looseness of the tape is removed by rotating the reel bases, since the reel bases continue to rotate as the motor rotates, during ejection the cassette is raised while a force is applied to the tape by rotating the reel bases. Consequently, when the cassette leaves the reel bases, it leaves one of them earlier than the other. Consequently a force of the other reel base is applied thereto, or the tape is liable to be loosened by the inertia of the tape produced by the rotational force of the reel bases due to the rapid removal of the force appied to the tape. As mentioned above, in spite of the means provided for preventing the looseness of the tape, the tape is evenutally loosened, and as a result the tape, deviated from its normal path, is twisted, or folded, which was another problem to be solved.
In addition, recently, some driving systems are so constructed to be reversed, depending on the operation to be effected by means of a motor rotatable in two directions, normal and reverse. In this kind of tape recorder, if the rotation of the reel bases is reversed, as it was, at the moment of the reverse of the rotation of the motor, the tape is unwound. As the result, since the tape is loosened, in addition to the problems stated above, there is another problem regarding how the reel bases can be constructed so as not to be reversed.